If you are in England you can see a dentist for about £25 for an initial consultation. Most dentists in the UK are private rather than NHS so most people have to pay, but you should be able to see any local dentist as a temporary resident if you explain. There may be one attached to your college or university.
Using a steroid paste for a few days should not normally cause bleeding of gums. Ask your pharmacist for Corsodyl mouthwash to help with that. As the paste is topical the amount entering the systemic circulation should be minimal.
There is a mouthwash called Difflam which may also be helpful as it is anti-inflammatory. I usually recommend it for sore throats but it can help ulcerative conditions too.
Compeed have brought out new 'plaster' for coldsores. This you can use as a second skin over the canker sore. You may need to go to larger branch of BootsThe Chemist to get it. Otherwise use Vaseline as a barrier.
When you go into Boots, ask to speak to the pharmacist and show him/her your mouth that will get you a second opinion.
Regards
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