I have red marks on my side (flanks) after my SculpSure treatment. Can I apply arnica get on it.

Yes, you absolutely can use Arnica gel, which is a great topical for all kinds of skin pigmentation or irritations. Even without this though, the red marks should slowly resolve all on their own. This is not a common side effect with SculpSure, but is certainly not atypical. If it persists or worsens, you should contact your treating physician. Remember to massage the treated area for at least 5 minutes several times a day.

Mild inflammation is expected after sculpsure especially if there are stretch marks in the area treated.  Also small lumps or tenderness is common initially.  Be sure to gently massage the area daily and stay well hydrated.  Arnica should be fine to apply to the area after 2-3 days and usually will reduce any bruising.  Discuss the redness with your provider to ensure that a small amount of pinching with the frames is avoided- this likely could have resulted in the redness that you describe.