What is this golf ball size hard lump near my mons just below incision site?

It is difficult to say what this may be without a picture or physical examination. This most likely represents scar tissue. I recommend you visiting with your plastic surgeon for a detailed examination.

If my patients have questions after a tummy tuck I ask them to contact my office at once via telephone or email. A hard mass near the incision can mean infection, bleeding or other significant issues. Contact the office at your plastic surgeon 

What you describe is consistent with a postoperative infection. You should report this to your plastic surgeon immediately.

Hello!  Thank you for your question. Your description warrants an examination by your surgeon. The signs and symptoms of redness, tenderness, and increasing size are worrisome and could be consistent with an infection/abscess or infected hematoma/seroma.  Hopefully this is nothing more than scar tissue or a suture, but these signs are concerning and should be evaluated. Best wishes. 

The most common reason for a lump in this area is what is known as a stitch abscess.  The contents of this lump/stitch abscess are the dissolving stitch and the white blood cells that are helping it dissolve, but usually no bacteria.There are a myriad of other possibilities, but without an in person exam, none of your RealSelf team of experts will be able to give you any definitive explanation.In most practices, a superficial lump of this nature is normally lanced under local anesthesia, and at that point, the pain, the pressure and the redness normally dissipates.  At 3 months, one would usually see their plastic surgeon for follow up, and he or she would be the best person to diagnose and probably treat this painful, but probably not dangerous, lump.