Getting a chiropractic adjustment by a well trained Chiropractor should not hurt. People are usually more surprised by the pop sound after an adjustment.  During a Chiropractic Adjustment you are put in different positions which allow the Chiropractor to perform the adjustment correctly.  An adjustment is performed to the spine to restore motion back to an immobile segment of the spine.  The segment becomes immobile do to muscle tension compressing the joint.  The adjustment is performed in the direction that will easily open the joint and fast stretch the muscle which is causing the problem.  The adjustment is performed at a high velocity (quick) with a short amplitude (small movement) to free the joint without the muscle being able to prevent it.  After the adjustment is performed an audible pop sound is made as the joint surfaces separate.  When the joint surfaces open it causes a negative pressure in the joint fluid causing a nitrogen bulb to form resulting in a pop.  The pop sound is called a cavitation.  A chiropractic adjustment that hurts while being performed is due to either a sore muscle being under the contact hand during the adjustment or the patient not relaxing during the adjustment.  In either case the discomfort is only temporary.

A more common reason for any discomfort felt after a chiropractic treatment is due to the changes being made in your muscular tone.  After a visit the treatment changes the general posture tone which your muscles have to get use to.  Also locally in the area of the adjustment the new motion can cause muscles to be sore as they readapt to normal function.  If you experience discomfort other than general soreness it is important to talk to the doctor who treated you.  It is possible that you may need to get in sooner than your scheduled appointment.  I have found that when you start making corrections with someone who has been in pain for a long time they may have new pains after each visit.  This is due to compensations being removed during care.  When we have structural issues in our body we tend to develop compensations for the root problem.  The pain that initially prompted a person to seek care may be a compensation for underlying issues.  In the beginning of care we are correcting compensations which will cause the root problem to arise.