Halp! What did I do to my hip?

Yesterday I went to the gym after a month long absence. I decided it would be a good idea to start squatting right away. I started at 40 lbs just to warm up. It felt fine so I moved up to 50 lbs which normally isn't a problem for me. On my third downward movement my right hip flexor made a little pop and there was some pain when I came back up. I didn't want to risk injury so I stopped right there. Today my hip gets a sharp pain when I walk down stairs, but going up seems to be ok. There is a little bit of pain while walking, but not enough to make me limp. Anyone know what I did? I'm afraid I tried to jump back in too quickly