that soreness is called DOMS, or delayed onset muscle soreness, and it's a good thing. when you work out, you stress the muscles to the point of tearing just a little bit. that soreness is them healing and getting stronger...which means you had a good workout.
you can keep working out if your muscles are mildly sore, but if they are tender to the touch you are better off going with some active recovery, like a good walk, swim, etc. Eventually, as your muscles get stronger and adapt, that soreness will go away.
keep up the good work.