Broken brackets- these can be left until you are able to see your orthodontist
Ulcers/ mouth irritation from the brace– wax is the best treatment in these cases. It is important to dry the part of the brace which is rubbing your cheek to allow the wax to stick. You will need to mould the wax around the brace to prevent it from coming off. It is recommended that you use the wax for at least 2-3 days to allow the ulcer to heal. Your cheeks will heal quickly, and usually heal with more resilience.
The brace should not continuously break, if this does happen then you might need to check your diet to ensure what you are eating is brace friendly.