"Your SIM cannot be accessed. Please call your carrier to obtain your PUK code." error on my iPhone

So did you contact your carrier? Assuming that you have forgotten or misplaced the code, they are the only people who can help you with regards to your current SIM.

Use a SIM PIN for your iPhone or iPad - Apple Support

"Never try to guess a SIM PIN or PUK code.  The wrong guess can permanently lock your SIM card or eSIM, and then you would need a new SIM card or eSIM."

as it states if it request the puk code and the carrier you use do not write the puk code on the sim card then you need to contact the said carrier before you can access their cellular services again

yes for your sim card

you can read more about it here

Personal unblocking key - Wikipedia