As a Glosters, DERR, R Berks, Wilts, RGBW or Rifles veteran, welfare cases, once initiated, will be handled by Rifles HQ in Winchester. However to initiate a welfare case it must be case worked either by SSAFA or Royal British Legion. They will then put your case to the Association for consideration. Regrettably this will not be a quick fix.
For RBL you need to phone the helpdesk on 0808 802 8080.
If that does not work then try this hyperlink https://www.veteransgateway.org.uk/ and work your way to the page that is relevant to your situation.
Another link for information is https://www.gov.uk/claim-for-injury-received-while-serving
If the case is due to an injury that was due to service duty, to prove that was the case you may have to request your medical service documents to be forwarded to your GP. Your current GP surgery should be able to advise how to do this.