Hi i have blood blisters that occur on the inside of my thigh. I am 20 yrs of age and a male. I have not been tested for STDs and have had multiple sexual partners, not a lot, but at least 4 or 5 unprotected. They occur on both sides, mostly the right though. As of now I have 2 at once. If messed with they become sore, otherwise aren t very bothersome. They are always blood-filled and never contain puss. I sometime have a slightly painful urination, which is a stinging like feeling, but not very often.