Tightness on one side of forehead after Botox. Is it possible that my doctor injected more Botox into the right side?

Botox can take a full week to take effect.  I would wait the week to see how everything settles out.

It is possible that one side of your forehead responded differently than the other.  However, you should wait 2 weeks to adequately assess.  Botox doesn't always "kick-in" evenly over time, so it may be pre-mature to tweak the treatment at this point. #botox

Hi
there, thanks for your question. I generally recommend that patients wait
about ten days for Botox to take full effect. However, keep in mind that
muscle movement at one area can be stronger than in other areas so it is
possible they did inject more in one spot than another. Should you still
have questions after ten days then reach out to your provider directly. -Dr. Coan

I would wait another week or a little longer and see what happens. If you still experience the same symptoms go back to your physician. If you are still not satisfied then I would consult with an experience dermatologist or plastic surgeon. I wish you luck and would appreciate your feedback. 

Please contact your doctor to evaluate your problem and discuss your options. Hopefully, your doctor is an experienced Board Certified Plastic Surgeon.