DOMS- and i'm not talking champagne.

Delayed Onset Muscle Soreness, commonly referred to as DOMS is the gradually increasing discomfort that occurs 24-48 hours after an activity.  The pain is a result of stressing the muscle beyond what it is used to.  For someone who doesn't lift weights on a regular basis, DOMS can occur from something as simple as push up sets or even a toning/sculpting class.
I like to refer to DOMS as "the good pain"- it means your muscles are adapting to your fitness regimen. When I wake up the morning after a hard workout and feel pain in my triceps as I brush my teeth, I know good changes are happening to my muscular structure.
Just because it's OK or even good to be sore doesn't mean it's comfortable.  Ways to alleviate pain include: ice, rest, advil, heat and stretching.  Stretching is incredibly UNDERRATED-- it helps break the cycle of soreness to muscle contraction and tightness.  Remember after long runs or hard bike rides to cool down.  A good rule of thumb is continue walking/jogging until your heart rate has come below its working zone.
Take it easy a for a couple days while experiencing DOMS.  Light jogging, swimming, spinning with low resistance are all great options.  Don't expect to PR during the 24-48 hours after a hard muscular workout.  Instead, allow your body to recover properly and work to prevent injuries by listening to your bodies needs, wants and most importantly, its discomforts.