I don't think it is a criminal offence but it is definitely a misuse of the visa. You should have first gone to the country that issued your visa. You may be denied your next visa or have the next one issued for a shorter term/single entry or asked for an explanation of why you never visited the country that issued the visa. I don't think you can do anything now to mitigate any consequences for you (if it even comes to that). The rule is that you should have entered/visited the issuing country first. Did you originally plan not to visit the issuing country but applied for a visa there because it was easier to get or did your plans change?