Small Red or sometimes Purple bumps on head of penis

I'm an 18 year old guy and i'm not really sexually active. I've had unprotected oral sex from two girls and I don't know if either were clean or not. Both times were about a year ago. I've noticed within the last about 2-3 months that I've had about three  small bumps around the head of my penis develope. They are normally a red color but sometimes turn purple. there is no white on them. I honestly dont know when they developed and they could have been there a long time or not very long, I'm not sure. But anyways I have had no pain urinating or any irritation so i'm curious to know what this is. I don't think its a STD but i dont know much about them and i wanted to check it out without going to a doctor. If anyone can help it would be greatly appreciated.

Taylor