Prayer Limits

I've been having conversations lately and at some point in the conversation, the topic of prayer has come up. I have a question. When should we pray? What should we or should we not pray for? I recently cut my finger pretty bad and it really hurt for about an hour. I wanted to ask the group of guys I was with to say a quick prayer of healing or just prayer about it, but didn't because I felt like it wasn't significant enough to pray about. Is that fair? I feel like it's not. Do any of you struggle with situations like that? What's your opinion?