Hello and Welcome to just answer.
I am sorry to hear about your discomfort.
Until you see your dentist,you can use “Dentemp” at home to fix your crown.
It is a traditional dental combination of zinc oxide and eugenol (clove oil) mixed.
You can use it to re-cement your cap. It is a strong material and will provide good adhesion. It is also used as temporary filling material.
Have a look at these sites for more information: http://www.majesticdrug.com/dentemp_os.php
I hope this helps!
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