How is the pain if you stand on the injured hip/leg and jump on one foot? More pain=bad sign. That said, many things can be run through, and then get worse. Rest/ PT is usually a good choice. But, the reality is, it depends what you're dealing with.
I'm in my 30s.... ran through a bout of patella tendonitis in HS (an easy to treat injury) Didn't treat it, didn't rest it, didn't ice it, didn't do any PT... ended up with a screwed up knee that made me miss all of track season. Had I treated in early in the injury, problem would have been solved quickly. Now despite all this, I'm still running decades later, so odds are you'll be fine. But early season injury - especially if you are ramping up your mileage after a summer of lower mileage/limited speed work... it all points to some sort of easy to treat overuse injury that you just want to ease back into things with.
If you're got the MRI scheduled, ice as the earlier poster described, get the facts, and you'll be fine by the time the races you care about are approaching.