My puppy has a big red spot on his back leg, about the size of the top of my finger. it is raised and pretty hard to touch, doesnt seem to have a head. It is a bit red as it looks like he has been biting it a bit. He is fine in himself and isnt biting at it all the time and it doesnt seem to be bothering him.
If it looks a bit like a big wart it may be a histiocytoma ( not sure I've spelt that correctly) . My dog one when he was 1 , if they leave them alone they go away eventually but ours had it on his leg and chewed it like mad and it grew so we had to have it removed which was a bit of a saga. On the plus side they are not ,according to our vet , supposed to recur.