Can I get a body massage 3 hours after getting Botox in my front neck area?

A massage limited to your body and not involving your neck area should not be a problem 3 hours after having received a Botox treatment to the front of your neck.  

I generally tell my patients to wait 24 hours before having a facial massage after Botox.  I would check with your physician and confer which areas were treated and if they think it is safe to have the neck massaged.

I typically suggest that my patients wait 24 hours after
their Botox treatment before getting a massage or performing strenuous physical
activity. There is the possibility that the pressure applied to the body during
a massage can alter how the Botox is distributed and affect the aesthetic
outcome you desire.

Botox can migrate (spread) after injection, especially when pressure is applied. There is a risk that if this happens, you may not get your desired result. Ultimately, you should discuss your plans with your injectionist and receive clearance from them before proceeding with your massage.

After Botox you do not want a facial or  massage of the treated area.   If you had forehead Botox I would not want you lying prone either.  Since your Botox was to the neck you should be fine with a massage but not to the neck area.  My Best,  Dr C