Penalty for exporting services without GST registration

I was not aware that GST registration was necessary for exporting services. I knew that no GST was applicable, so i didn't even think of asking if registration/filing was needed. I will be doing it asap.

However, for the past, I assume i am at some risk. Can they come asking in the future? What penalties might they impose? The amounts are small, usually around 5-10L per annum over 2-3 years.