It's pretty common for just a nozzle swap to warrant a small adjustment in your probe z offset.
Depending on how you have your firmware setup, the adjustments may be able to be done on the lcd. Otherwise, if you have it connected to a computer or octopi, you can use the command below. Either way, you won't need to update firmware each time, only the first time to install a bltouch.
that's for a minus 1.0mm offset, adjust that number for whatever you need, may need to test and rehome (G28) a few times to get it just right... after you do, make sure you do M500 to save that value to eeprom so it isn't lost when turning the printer off. alternatively, you can put that in your start gcode and not have to save it to eeprom.
There are lots of examples about configuring a bltouch already out there, probably plenty in this forum (I actually may have posted some code a while back, can't remember). It'll depend on what board and firmware version you are using. If you are up for it, it may be a good time to do a complete firmware upgrade to Marlin 2.0...
I can give you my firmware code that has a bltouch, but its a heavily modified FT-5 with and SKR 1.3 board and BMG-clone extruder, so it won't be exactly plug and play... Let me know if you want it, I have it on github and will just have to grab a link.