|It may be a cultural thing, but it's also a sexual harassment thing. This is unwanted touching, and there is no cultural wildcard that gives sexual harassers a free pass, in all senses of the word.|
Depending upon your working relationship with this individual, one approach is to directly tell him that this behavior has to stop now. Describe exactly what he did to you, let him know how you feel about it, and insist that it end. You should also mention that you will get additional help if it continues.
Look also at your company's sexual harassment policy if it has one. There should be an internal procedure to deal with this situation. Either way, if the harasser ignores your comments, you should discuss the problem with your manager or with your company's human resources representative if there is one. In the event that you have to take further action, it will be very important to demonstrate that you reported the problem.
If you find that the situation cannot be remedied internally, your next step should be toward your state's fair employment agency.