Whereabouts are you based?
Have you contacted the train company yet? (Twitter, phone, live chat)
If you live near an East Coast ticket office, there's a fair chance they'll be able to regularise your tickets at no cost. Failing that, they're normally willing to excess the discount away at a cost.
Additionally, common sense is applied more often by certain train companies than others. Asking a Scotrail guard before boarding, for example, might not be an issue. Travelling on Northern without the right ticket is virtually asking to be slapped with an £80 bill or prosecution.
Did you buy it online? Transpennine Express were happy to refund me wrong-railcard tickets (Advances for VT, no less!) on the condition I bought the correct-railcard tickets through their website. Contacting customer services is definitely worth trying.
But if the ticket only costs a few quid I personally wouldn't bother; I'd just buy a new one.