What is the red bump on my dog's eyelid?

I'm thinking that it formed overnight, because I just noticed it this morning and from what I remember he was fine yesterday. He's not itching it or anything, he seems to be oblivious to it. I clean his eye boogers out regularly (gross, I know, but I just can't stand the look of boogery eyes if you know what I mean), so could that have caused it? And is this common/serious?