What Causes Pain On The Right Vaginal Lip?

I'm 22 years old and last night I was having some pain on the inside of my right vaginal lip. I went to look to see if maybe I somehow cut myself shaving and saw a lump there. At first it looked like maybe I cut it and it just got swollen but it does't appear to be cut. It looks more like I pinched a piece of skin and it turned into a small blister. It is rather painful though. What should I do?