Will be physically incapable of sexual activity, plus, with rough technique, the formation of narrowing of the urethra with scars is possible.
with traumatic, rather than surgical, amputation may die from blood loss
Here, for example, what happened to an American named John Bobbitt https://ru.wikipedia.org/wiki/John_and_Lorena_Bobbit he married a feminist, with easily predictable consequences. But doctors sewed back the severed organ for him, and John even appeared later in pornographic videos. I don’t know if Russian doctors could have done this.
The moral of the story is obvious: men, never sleep with feminists, under any circumstances.
If you cut off the penis, with a high probability, it will become absent. (amazing!) If you cut off the rest with it, then the production of testosterone will stop, as a result of which the man will recover, there will be no libido. Well, in general, nothing interesting.
Does your question have any practical application? If you just cut it off, there is a chance of bleeding or catching an infection while trying to bandage. If the penis is properly amputated with the reconstruction of the urethra, then, apart from difficulties in sexual activity, this will not lead to anything else. Amputation of the penis is not the rarest surgical procedure in the world.