We have the exact same problem with Brody. It's a little scary. He doesn't like the other dogs sniffing him. He tries to run away from them. The bigger dogs seem to think it's a game and try to catch him. It freaks him out even more. I'm afraid it will excited the bigger ones too much and he'll get hurt/attacked. He ends up peeing on the run trying to get away from them.
Does something like that get better? He use to love meeting other dogs until some bad experiences in our neighborhood. I was hoping the dog park would help him become more social. It seems to make it worse.