My son had a choking episode a few days back. i was told to watch for fever. he now has low grade fever and diarrhea. coincidence or from aspiration?

Maybe coincidence...: Aspiration can range from penetration of larynx with saliva or small amount of swallowed liquid (just irritates vocal cords a bit) to frank aspiration pneumonia (think of it as a non-infectious chemical burn of lungs from stomach acid). Neither scenario should result in diarrhea, but instead hoarseness, dry cough, shortness of breath, etc.Your son needs a chest x-ray, & further medical evaluation.

Viral likely : He mist likely has a a viral illness. If there is a lingering cough or fever that persists longer than three days, please see your physician.