Can tanning in uv light cause scar tissue to worsen?

Yes. Tanning can make a scars appearance worse due to the fact that scar tissue has less melanin than normal tissue.
Yes it can... But please be aware that scars will fade with time and take 6-12 months to mature. In the meantime, avoid sunburn or suntan while the scar is still pink. Otc medications such as mederma may help to improve the appearance of the scar. Scars often look their worst about 6 weeks after the injury. If the appearance worsens after that, you may want to see your doctor.