Hi. Tooth eruption is a slight painful process.
You can take any regular painkiller (not for long durations) and also apply local numbing gel on both the gums as well as on the ulcer.
If very painful, please visit a dentist who would clean that particular tooth deeply ( a very simple procedure).
If something is coming between your teeth while eating and speaking then you need to visit dentist and get it treated as it might eventually swell.
Next Steps
Visit a dentist at the earliest.
Health Tips
Warm salt water gargling will also give relief. Take care.