It probably would have been better to take the engine out and pop the backplate off then clean it out thoroughly. As far as damage, probably some, but if it is running then it should be ok. You probably took some life out of it though and some performance also. At least the filter problem was caught early. Worst case you will have to put a new Piston/Sleeve in it ,and maybe a bearing, sooner rather than later or just get a new engine.