I had mono a couple weeks ago and im noticing a resurgence of a sore throat, is it alright to go to the gym or is that a bad idea?

Might be infectious or contagious. A recurrence of throat pain can be from a strep throat infection (antibiotics are needed), a cold or influenza (antibiotics usually not used), mono, COVID-19, allergies or irritants, etc. Usually, a person sees the doctor if the sore throat is bothersome or doesn't go away quickly. One should not simply assume the cause is mono, as it could be a different cause.