What does an at home fingerstick reading of 423 and 241 mean?

Very likely diabetes. You need to be checked for diabetes. Especially if you are having symptoms of diabetes out of control, such as, excessive urination, thirst, and/or hunger. If you have diabetes it is not controlled. Either way you need to see a doctor and soon.
High blood sugar. Blood sugars can be tested by using a "fingerstick" prick and a device that checks the concentration of sugar in the blood. Normally well below 200, thus 423 is very high and indicates poorly controlled diabetes and 241 is mildly elevated.