I had corona virus mid december, and have felt healthy up until now, i am now experiencing sneezing, occasional nasal congestion, sore throat and diarrhea, and a dull headache?

Need to examine: It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. The two issues are likely not related. It would be prudent to see a doctor. Wish you good health!

Symptoms: This could be one of many viral infections. The best way to try to figure out the cause is through a medical consultation.