How long do I need to wait to have more liposuction on my chin to make it even? Its been 2 months.

It is not unusual that there could still be some swelling present 2 months after liposuction under the chin.  An examination of you would be helpful to try and determine what might be causing the unevenness that you see in your neck.  If it is fat and not something else, I would recommend waiting at least 3 months from the time of the surgery before doing any revision surgery.  It is possible the uneven appearance you see is not due to fat, so a different treatment might be needed in that case.