I do not wish to sound rude but people can not help you if you do not give the basic answers to simple questions you are being asked.
You asked what you should do now in your original post. To advise you what you should do now you need to give some more information
These questions are:
1) The stations where you started & finished your journey;
2) The stations where you changed trains (if applicable);
3) If you presented a ticket(s), the information stated under "Ticket type", "From", "To", "Route", and any other relevant details;
4) Uploading copies of any paperwork (with personal details redacted) with your post, that you may have been given or received to date.
5) which part of the journey did the staff member photograph your railcard / speak to you (do you remember what station it may have happened after for example, especially fi you changed trains on your route)
If you want to know what will happen next it will likely be along the following lines:
A) the railway company will write to you about the forged railcard and threaten you with taking you to court and prosecuting you
B) the letter they will write will ask if you have any explanation for what you did or mitigating circumstances - it is vital that you get this letter and reply to it
C) The railway company will consider your reply and decide what to do next
D) They will look at all of your ticket buying on line from wherever you bought tickets and they will notice any other tickets bought with a Railcard discount and they will presume these were all bought with the forged Railcard - they will want all the money for those journeys
E) They may take you to court and prosecute you for which you will receive a fine, costs and other sums, as well as a criminal record.
or
F) they may decide not to take you to court if you pay them a sum of money to put right what you have done wrong and the fares you have avoided. This is usually called an '
out of court settlement' - this is a better outcome for you than being taken to court, and would be the one that I suspect you should seek to achieve if you can do that.
If you do not want to provide any further information here that is up to you. You can see if you can discuss it with your university / college / student union to see if they can help, or you could go to see if a solicitor / lawyer can help, for which you will probably also have to pay a fee to the solicitor for their time and any work they do to help you.
