Hello and thankyou for this picture. Not coming into contact with other dogs is great for preventing infectious diseases (although doggy contact can be important for socialisation reasons. I don't know your dogs' vaccination history but please do ask your vet about this because the puppy socialisation window is limited). However, not all changes are infectious. I'm not sure what your concern is here; I think we are looking at the hair follicle for one of the stiffer hairs on the muzzle and it could be completely normal. This looks to me to be the most likely. However we might also be looking at the reaction caused by a demodex mite, a small spot or pustule, a very small lump or something else. Is there one on the opposite side? Please do show it to your vet.