Extremely Tight Hip Flexors

I was traveling and had to take 4 days off running in a row. I was back last night and did 5 miles on the treadmill (it’s gentler and helps lessen my sciatic pain). By mile 4 I was so tight in my hips and butt, and today they are still tight and sore. Not even sure how I will get a run in tonight, since it hurts to walk.

12w4d.

Any good suggestions for preventing/easing? I’m guessing there are plenty of stretches I should be doing, but figured maybe someone else had a similar problem and could tell me what worked for them.