How do you treat and prevent a sore quad muscle?

Alternate heat and cold and MILD stretching. Try some Bengay to reduce the pain. Unfortunately, the only thing that can really heal your muscles is time. Depending on how badly you injured the muscle, I would say about a couple of weeks. If the pain is somewhat mild (if it doesn't affect your daily life - walking, getting out of bed, etc.) then I would say about a week of recovery. Make sure to take care of it! Try not to over exert yourself! I've found that baths tend to help a lot. Especially before bed, to relax the muscle from a long days work. I've injured myself far too many times to count. I know how annoying it can be! Hope everything works out for you!

It could be a strain or just over exertion. It may also be normal wear and tear of the muscle that just hasn't completely healed yet. Muscles get microtears every time you exercise them. Thats why it is advised to not work out the same muscles every day.

I had the same type of feeling in my quad from cycling because I didn't give myself enough time to rest and heal. I would suggest taking a short break from working out (or at least not working out the legs) for maybe a week and see if that helps. If not, going to see your doctor will be better treatment than advice on here.

Before your running ensure you warm your legs up and stretch. Afterwards go for a light jog/walk to relax your muscles and ease the lactic acid.(lactic acid is the reason you have sore legs) and stretch afterwards. If you do that and your legs are still sore the next day a swim is good thing to relieve tension. Especially at the beach because salt water is very good for the muscles (hence why the football players go). Simple relaxing walking the day after your run is a good thing to relieve tension too. The only bad thing to do after running is "nothing" :)