Consistent Pain in left Hip

Hi! 

I have been running for a few years now, and have consistently been running half's for about a year (every 4ish months). I went for an easy long run, about 8 miles, 3 weeks ago and towards the end felt this pain in my left hip/outside glute. Since then, walking is sometimes painful. I tried to go for a run about 2 weeks ago, and walked every time it started hurting-only ended up going about 2 miles. 

Not sure what this is or what I could/should be doing to recover? 

Thanks!!