If it's a large fan-out clock, you'll probably want it on a global, so it will route from the regular I/O to the global. Not the end of the world and should work fine though. Note that your I/O delays will be different(longer Tcos, shorter Tsus). You won't be able to drive a PLL to shift the clock. (I actually, I don't remember if you can drive a PLL with an internal signal or not. Used to be illegal but may be legal on newer families. Try it if you think you might need it).
