strange itchy bumps on skin

[Benny Z]

i was in my tank moving corals around and pulling off hydroids on monday after work. was in the tank for probably 20-30 minutes or so and brushed up against all kinds of things (corals, rock, micro life). at one point i remember feeling a stinging sensation on the underside of my right forearm, but didn't think much of it.

ever since, i've had these little itchy red dots that look a rash on my forearm. any idea what this could be from???