I've had my belly button pierced for about 2 months and I noticed its really tender around the piercing but its not a really bad pain. There is redness around it and to me it looks like a blister on one side of the top part. If you can let me know if its infected that will be great.

How can any of us tell you if it's infected or not. No one here is a medical doctor, we can't practice medicine over the Internet, and we can't see the piercing and poke around on it. What you are going to have to do is go to your doctor and let him take a look. I know, I know. You wanted a quick, free answer. Well, you have trouble, you said, with tenderness and redness and a blister of some sort That sounds like a developing infection. Time to see a doctor.

i've had my belly button pierced for about 2 months and i noticed its really tender around the piercing but its not a really bad pain. there is redness around it and to me it looks like a blister on one side of the top part. if you can let me know if its infected that will be great.

Yes, I believe your wound is infected if it's a) reddened, especially if progressively worse; b) tender, c) draining drainage which is opaque, or has pus in it and possibly, d) you have a fever and/or feel generally sick. The blister is not normal, either. You should have it checked by a health professional, and in the meantime, keep it clean 2-3 times daily with soap and water.
--RN x 32 years