Whenever i enter my sim card my iphone shows invalid sim option I purchased it secondHand and now it’s completely useless it’s carrier locked how can i remove carrier lock from my iphone?

You contact the carrier the phone is locked to and request that they unlock it for you if possible. See if this helps: How to unlock your iPhone for use with a different carrier - Apple Support

You cannot remove the carrier lock and neither can Apple.

Only the carrier can remove the lock, so you will need to get in contact with the carrier to which the phone is locked and ask them to remove the lock.

Please understand that they may be under no obligation to do this, but you might be able to set up service with that same carrier. To see the carrier to which the phone is locked.....

Settings > General > About > Carrier