HELP!!! FTM-baby's temp 101.4 temporal 102.1rectally

NO other symptoms. My son is now running a fever. The little boy I nanny had a low grade fever with no other symptoms a few days ago which I didnt go in that day just in case but it never turned into anything. Now my sons temp is higher than it's ever been basal temp (97.4-98.6)but he has NO other symptoms and is his normal happy self. I can't think of anything it could be! What do I do?! he is 5&1/2 months. I'm a FTM