fall in public car park

whilst walking through a car park of a retail park earlier today, i stepped off a kerb and stood right on a piece of scrap wood with a nail sticking out of it (looks like a piece of a pallet), this went into my foot and caused me to sprain/twist my ankle and although i realise its only a minor injury, this now makes it painful for me to walk and is probably gonna result in a tomorrow off work. i am working away from home on my own, am 20 miles away from nearest A&E so the prospect of driving myself to hospital and spending the next 3 hours waiting really doesnt appeal to me. having said that, the idea of losing a days pay doesnt either. I want to make a claim for this but really dont know if i have a case.