I Was Weeding Around My Fence On Sunday Afternoon(I Have

I was weeding around my fence on sunday afternoon(I have a bad knee and was bent at the waist to do this) and when I went to bed later that night pain radiated from my left buttock down the side of my leg. I could not find a comfortable position and was unable to sleep. Monday I did not go to work as I sit all day and I did not think I could do it. Tuesday I went to work and tried to get in to see my doctor, but he was booked, so I went to another NP and was told I has strained a 'band' that ran along the side of my leg. I would like to know what band this is and what should be done for that.