Recently I've started noticing one of my upper arms, getting thicker than the other! I believe it's my triceps, as the biceps look pretty equal in size. It's really only noticeable when I tense up, with my arms accross my chest. Or, when I have a certain(tighter) tshirts on, one arm fills up the sleeve nicely, and the other doesn't, with a little space. 
I decided to give my bigger arm a rest, while continuing to work out the smaller one(I've been using dumbells), but I don't see much difference so far. So, is there any guidelines, or tips anyone could give me for trying to correct the problem?
Thanks.

I decided to give my bigger arm a rest, while continuing to work out the smaller one(I've been using dumbells), but I don't see much difference so far. So, is there any guidelines, or tips anyone could give me for trying to correct the problem?
Thanks.
