Right pupil is a bit larger than left, soon after waking up for 5 days. i had a concussion 3 months ago, i recovered in a week. should i be concerned?

Yes, implies brain: injury from concussion, though only issues commonly detectable by current technology would be large enough tissue damage (stroke) or intracranial bleed; possibly subdural hematoma. The latter occasionally becomes symptomatic slowly & progressively over time. Latest model NMRI scans, 1.5- 3.0 Tesla systems generally have the best sensitivity, Suggest finding assistance worthy your trust.