Brad, it is likely that you have some relatively minor irritation that will clear given time. For your own peace of mind do get tested as you suggest. In the mean time here is some information on mutual masturbation from a reliable medical source:
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Mutual Masturbation and Sexually Transmitted Diseases
Mutual masturbation is when you and a partner sexually arouse each other using your hands. It can also involve you each masturbating, but near each other. In general, mutual masturbation is relatively safe sex. That’s particularly true if no bodily fluids are transmitted.
There are, however, ways to make mutual masturbation even safer. If you are touching your genitals, you can wash your hands before touching your partner’s genitals—or vice versa. You can also consider using gloved hands to touch your partner and bare hands to touch yourself. Either one of these things makes it less likely that you would spread an infection between you.
In general, STDs that spread through bodily fluids—such as HIV and chlamydia—are relatively unlikely to be spread through mutual masturbation. There’s a bigger risk for STDs that spread from skin to skin, such as herpes and molluscum.