If he gets a fever, or if you start to notice a red line going up his arm from around the area of the bite, go to a doctor quickly. Not sure if the sneezing is related, but the slight numbness could just be irritation from the bite or it could have been near or on a small nerve like Dan203 said. Is it swelling a lot? A little swelling will be normal, but if it really puffs up, doctor.
It's probably nothing, but it's a good idea to watch it for a couple days. Did you wash it out very carefully with a lot of hot water and antibacterial soap?Scratch in there with a brush or fingernail with antibacterial soap to really get everything. If you're very nervous, try packing in sugar too or raw honey to help draw out other stuff the soap and water may not have got.