Honestly I don't know for sure but bumps that look like blisters make me think of warts or some other viral condition. Some people form keloids when they are bitten by insects of anytime they break their skin, which look red, swollen and blistered-like in appearance. It could also be cystic boils, or acne that's resistant to clearing up because of the location. It would be prudent to see a Dr since you don't know what it is.
