It's a cold and is a pain in the ass but doesn't warrant being sent home. 38 isn't even classed as a fever. The normal range is 36-38 depending on the individual. Just part of the job, as long as it is clear and the kid isn't haven't projectile sneezes or anything then you are going to have to just shadow him, sucks but such is life. I'd be pretty annoyed as a parent if is as called out of work to collect my child who simply had a runny nose even if it is constant and annoying.