I noticed three red bumps-about dime sized on Boogie-one on his head-one on his leg and the other on his lower belly...near "his package"

He happens to have a vet appt on Thursday for something else-not a health issue-so I can ask then, but I was wondering if anyone knew what it could be. The websites I looked at said a whole bunch of things...

nothing is coming out of it..
when I press them it seems to hurt, but not enough to make him cry-he just moves around to get me away from it...
they just appeared out of nowhere
he doesnt look like he is in pain