Well I found the ES while roaming, well I found a place I couldnt enter, searched for the key, got the key, and now have the ES, will this screw up my game? I have only done a little bit of the main quest.

You not only randomly stumbled across Septimus, while wondering god-knows-where, but also...accidentally...entered one obscure button combination out of millions possible and got the elder scroll? Please, teach me your secrets, oh unsung god of videogaming.

I went to the dungeon with the dwarven box, that needed a key, I googled the key, i went north of the college, talk to him, he gave me the key (not knowing what was in there etc), I went down. Went through blackreach, collecting the crimson nirnroots, got to that, and simply noticed that I could only push 2 buttons, and if I pushed them in a certain order the cube lit up, and another button opened, I pushed some more, and poof there it was. Took it, read it, then decided to load a previous game, unlock it, and leave it there, with the back door open.

also the one i found was in mzinchaleft

Nope, nothing breaks if you find it early. Just don't sell it to a certain orc before you have used it in the main quest.

You can't do that, anyway. Not until after you use it in the main quest.

I finished the entire main quest early. It didn't spoil anything. The side quests are tremendous (at least as well-crafted as the main plot), and you can just enjoy them without worrying over how they'll affect the main story.

Many people have stumbled upon Septimus outside the main quest before. It happens. The fact that this starts a Deadric Lord quest which just happens to also give you the elder scroll in the process can be viewed as either coincidence or cunning design. Either way, having something and being able to use it is not the same. And seeing as how you can't use it until you get to that part of the main quest you have nothing to worry about.

yeah i found that "ES",but what does it do,i opened it,everything whent blurry,and thats all,whats it for.

It is used at some point in the main quest.

In some parts of the game with my first character,i got some items before talking to the guy that ask you to give that "certain item".Normaly when this happens there's a dialogue like(this happend to me with the golden claw quest).
-"Oh you mean this"
-"I found this,i'ts what you're looking for"?

neither one is that difficult to find.

you can find septimus' cave pretty easilly if you like exploring, its not like its hidden away

the elder scroll puzzle is not that difficult to unlock by pure luck either. first of all, it isnt exactly a "combination", you can just spam the buttons sequentially starting from right until they open up the buttons to the left. its not that hard to figure out randomly (this is how i "figured out" the puzzle the first time).

The Op had to accidentally find the Elder Scroll early, but I'm such a videogame ninja that my character started the game with five of them in his inventory.

Apparently I got busted while robbing the library in White Gold Tower and they extradited me to Skyrim (even though I'm a Dunmer), and they just didn't have the balls to try to take them from me.

They also keep calling me "Chuck Norris", whatever the hell that is...

yeah, i just hoped it wouldnt mess up the game like some things in morrowind did. I cant recall some items I had, but people walking by would comment on something being done etc.

I'd just like to mention that it weighs 20 lbs...

Quest items weigh nothing, even though it says they do.

I found the ES way early in the game and realized it was a quest item when I couldnt store it. So I just kept it and waited. I dont remember how I figured out the cube key, I just hit a few buttons and BAM it was there. Lol