If you cannot get it back in by loosening the radiator and moving it out of the way a bit and heating it, then your only option is to remove the camshafts. You have learned the hard way, just because it comes out with a bit of wiggling does not mean it will go back in as the forces applied are in a different direction and the inside of the tunnel is not exactly smooth. Make sure you don't crack it

which is why you need to heat it as it will be
less prone to cracking.
I am surprised you got it out with out removing the exhaust cam.

If you have to go the camshaft removal route make sure you have a torque wrench to tighten the camshaft bolts.
No easy answer to this one unfortunately, good luck