It is possible for filler to cause veins to become more apparent. The appearance of the vein should diminish as the product starts to absorb.
You have an option of using hyaluronidase injections to dissolve the product. Hyaluronidase will cause you to lose the volume of the product.
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It is possible for filler to cause a compression of low pressure veins, possibly making veins upstream of that compression engorge and appear more prominent. It will likely resolve with time as the filler degrades, and massage may help. The beautiful part about hyaluronic acid fillers is that they can be dissolved. If you want to dissolve it, find a dermatologist, oculoplastic surgeon, facial plastic surgeon, or plastic surgeon who is board certified in one of those 'core four' cosmetic specialties and has experience with hyaluronidase.