Were you running mostly with a forefoot strike (i.e. landing on the balls of your feel rather than your heels) on the hilly parts of the trail run? If so, you have used muscles you don't normally use for running and it is normal that they are sore.
phew that's a relief. I think I probably over stretched myself as I'd never done anything other than run 5k on the flat before. The achiness is worse when I'm sitting down. I might venture out for a gentle jog later and see if that helps.
My brother has run marathons and all sorts but only on flat(ish) concrete. He did a 10k cross country one once with me and he was aching for days afterwards, he just wasn't used to it. Nothing wrong with your legs
Egg, might be 'DOMS' from the hills, delayed onset muscle soreness, afaik it's not all the well understood but tends to happen when you do something that your muscles arent used to.
I find the best cure is to repeat the activity which caused it but at a much lower intensity, so in your case that'd be a bit uphill walking, I do some running but most of my experience is in weight training so it may not be so relevant in your case
Or you've just pushed yourself, a bit far, ie beyond your capacity to recover.
A regular stretching regime might help. Hopefully other posters with more running background will be able to give better & more specific advice
Help please...I'm fairly new to the world of running having recently graduated from the c25k programme. Last week I did a 10k cross country trail that included a lot of up hill bits (I walked these bits) and my legs are still aching 5 days on. What is going on and is there anything I can do?