As long as it's not excessive - having some lactic acid build up and post exercise muscle soreness is actually a good sign. You just don't want the pain to be extreme or to be lingering around for more then 2-3 days as that's a sign you aren't recovering from your workout.
Usually - if someone has excessive muscle soreness, they aren't eating enough protein.
Protein after all is what your muscles are made of and it's what is needed to repair and build muscle tissue.
Aim for 1g of protein per pound of body weight. If you struggle to eat enough whole food protein, you could consider using a high quality pure whey isolate shake. The one I use is called wheytobuildmuscle from n2bm.com