I am sorry to hear about your problem. Where exactly does it hurt?
Monk is right, and I join him in that I would strongly suggest that you do not play on Sunday, since it is almost impossible not to play tense and stressed on a competition. If you already have the beginnings of an injury that would be a sure way to make it into a full fledged injury. Many of these injuries may take years to heal, if they heal at all. Consider if it is worthwhile to risk having the next 2 – 3 years being unable to play at all.
As for you parents and teacher, (although I am amazed that they would suggest you play irrespective of an injury) they may be ignorant of the issues involved (maybe they have a “no pain, no gain” attitude). I suggest you print the helpful material in the two sites below, and give it to them for reflection.
https://www.ismennt.is/not/sen/musmed.htmlhttps://pianomap.com/injuries/Meanwhile, drop the virtuoso repertory and concentrate on physically unchallenging pieces but with a high degree of musicality. (I am afraid no Prokofiev toccata for a while!).
I also suggest that you consult someone who actually knows about this stuff and specialises on pianist’s injuries: most medical doctors are completely hopeless: they will give you anti-inflammatory and painkillers. I cannot stress this enough: Do not take painkillers. Without pain you will be doing movements that will make the situation worse. The pain is there to protect you: it will not allow you to make movements that will aggravate the condition further.
Leon Fleisher stated in an interview how bitter he was towards the medical profession. Most of the advice he got (and unfortunately followed) was wrong, Including a couple of unnecessary operations. It took him 30 years to go back to (sort of) normal. He reckons if he had gone to someone who actually had experience in treating this sort of condition, he would probably recovered without need for operations in about a year. His other mistake (according to him) was not to take the situation seriously enough in the beginning and just hope that it would go away by itself, and he just kept practising the way he always did (which was clearly incorrect), until disaster struck.
Read about it here:
https://www.cello.org/heaven/disabled/fleish.htm(and if you google Leon Fleisher, you will get over 20000 links!)
I wish you all the best,
Bernhard.