If you truly have sinusitis, this is visible on CT or MRI scan, and is treated with decongestants, antibiotics, steroids, surgery, irrigations, Neti pots, and a host of over-the-counter nostrums! If you have true sinus pain, pressing and lifting your brow should cause no (good or bad) change whatsoever. However, as has been suggested by others, this pain may be caused by stretching nerve or muscle fibers that results in a form of relief.
I would consider a trial of Botox in this area to see if relaxation of these muscles causes relief. If it does, a trip to a neurologist or pain management specialist may be appropriate if the pains persist.
Have a browlift only if your brows are too low and you wish cosmetic improvements to this region. Do NOT expect any improvement in your "sinus pain" from browlift surgery, nor should you ask for insurance reimbursement for this.