Laser veins removal: bigger blue (dark) veins as side effects ? Will it disappear? (Photo)

Laser treatment doesn't remove veins, it injures or destroys them so that the body will eventually reabsorb that injured tissue.  The appearance of your vein is now blurred and indistinct, so I expect that it has been injured and will eventually fade away as the body does its repairs.  Usually, laser treatment alone for surface spider veins is not enough, and injection of a solution to destroy the inner wall of the vein is needed. It is rare for a single treatment to successfully erase a complex of spider veins, so you may need t return for another treatment.    

It looks like the laser is doing its job and the vein is coagulating under the skin. That is what gives it the dark blue appearance.  It can take a few weeks for vein clearance in the legs post lasers. Sometimes a second and third treatment are necessary for complete clearance. Sometimes the veins decide not to listen at all. At this point I would wait an see what happens and not worry at all.

Laser for spider veins is performed routinely. As the physician surely discussed with you, it will look worse before it gets better. This thromboobliterative process will heal over time and it is important for you to wear compression stockings over the treated areas.If you have concerns, discuss it with the treating physician and return for follow-up.BestDr. Karamanoukian

What your pictures show is a clotted vein following treatment.  This is normal following sclerotherapy or laser vein treatment.  I would follow up with your treating physician to see if they would evacuate the clotted blood.  This would expedite the healing time.