You won't harm it, assuming you sanitized the wine thief or turkey baster when you took your sample.
I always think about what I"m going to do about any readings I take. If I'm going to make sure fermentation started, for example, a reading like you took is just fine. If I'm waiting to see if the beer is done, I'll wait a few more days before checking the gravity.
I normally leave the beers in the fermenter for 10-14 days, so unless I"m concerned that there is a problem, I normally don't check the SG unless I'm planning on doing something- packaging, dryhopping, etc.
But you didn't do any harm by checking now! It'll be fine.