What do I do for hyperpigmentation after laser hair removal?

It is uncommon to have hyperpigmentation this far out from laser hair removal; however, it can and does occur. I agree with trying bleaching creams that are combination with retin-a like Triluma, for example. I would talk to your doctor and use them twice a day typically is normal and avoid any sun exposure on those areas until they resolve. Alternatively, you might discuss with your doctor the use of a Q-switched laser to lighten the hyperpigmentation if it does not respond to topical treatment.

Before you address your treatment, you want to make sure the coloration which persists on your abdomen, is pigment.  Sometimes it can be checked by a dermatologist and if it is considered to be a pigment, then a Wood's light may determine if the pigment is superficial and probably responsive to treatment, or deep and sttuborn.  The other consideration is if the color is redness and not pigment and it might then be blood flow causing the coloration. If that is the case, then the V-beam laser or IPL might help reduce the color.
 

Thank
you for your question. It is not common to have hyperpigmentation for this long
after laser hair removal, but it does occur. 
You can use a prescription cream called Triluma to help reduce
pigmentation. Triluma contains a combination of tretinoin, hydroquinone and
cortisone creams, which helps to bleach your skin. Please remember when using these
creams to avoid sun exposure. I recommend having a consultation with an expert
to discuss your concerns and to determine the best treatment plan for you. Best
of Luck!