my cichlids tend to flick from time to time on the gravel and decor. unless he is doing it constantly i would not worry, just keep an eye on him. if it is ich, there should be other symptoms present. mainly the presence of what appears to be salt sprinkled on the fish.
flicking can be a symptom of any parasite, not just ich. the parasite lives in the water and is transfered from tank to tank by fish, contaminated water or equipment. the parasite is not visible to the naked eye. fish will show symptoms of the parasite when it is attached to the host fish. parasites can thrive in aquariums, unattached, for 7-10 days. once the fish stops showing signs of the parasite you should still continue treatment for the 7-10 day period following.
even though the 2.5 gallon is rather small for even a hospital tank, i would of left him in there rather than exposing him to the ammonia. watch for signs of toxin poisoning.
good luck