I Am A New Mom Of A Baby Boy. He

I am a new mom of a baby boy. he is two months old. I was changing his diaper and noticed a red lump in between his buttocks. it looks like it's filled with blood and puss. I am worried and would like to know what it is. It's a bit smaller than a penny. I had put diaper rash cream on it to prevent it getting any more effected. And it seems to bother him when he is laying on his back and it bothers him whenever touched. PLEASE give me an answer ASAP!