:)
Don't start!
seriously though, take it easy on downhills at first, get proper shoes, eat as soon as you get back from a run, if it hurts so much you need ibuprofen to run on it then you shouldn't be running, & remember to have a long-term goal of being able to run in 10 years, which is more important than whatever your current race is.
Oh, and never talk to ultrarunners, fell runners, or triathletes.