Muscle soreness doesn't mean that you've got a serious problem, it only means that you did something new, unknown for your body.
Basically, whatever you do new and unusual, in terms of volume, or intensity, or a neuromuscular pattern, involving new coordination, your muscles will react almost in the same way - they will get more tense over their usual range and try to prevent you from doing the necessary movement. There will be a clash between the new desirable movement and the old habits of the body. As a consequence muscles got pulled and over-pulled by their own body. The result of it comes as muscle pain.
How can you reduce your muscle soreness?
First of all, reduce the amount of new movement, the volume and intensity of exercises which cause the soreness, if the soreness is too painful. Then continue with these exercises to make your body familiar with them.
Second, do strength exercises for affected muscle group. Never forget to do strength exercises after your marathon
. They'll help you recover much quicker and more fully. Strength exercises actually return your muscles to their pre-race elastic condition, taking away their tension and spasms.
During the exercises you should come to reasonable tension allowing you to do 10 reps and more up to the point of getting the burning sensation in your muscles. The minimum number of sets is three, but you can increase it, if necessary.
After these reps of strength recovery I would recommend you to take a bath with apple cider vinegar (one bottle of 200-250 ml for the bath). It'll complete your recovery efforts for the day.