Last session a PC lost an arm (willingly) and he asked me if there were any penalties to his attributes like whether STR or DEX would be affected?
The PC is a Druid and lost his non-dominant hand. While losing an arm seems bad, mechanically speaking he can still spell cast and use his wild shape. Are there any rules in D&D 5e that addresses the impact of losing a limb? And to a lesser extent is losing an arm as bad as it seems for a spell caster?
The Dungeon Master Guide has an entry for such injuries, as an optional rule. In the specific case of a lost arm or hand the following would take effect:
The character can no longer hold anything with two hands.
The character can only hold one single object at a time.
Needs magic to fix the arm, such as Regenerate.
Nothing more is said on the matter, be it skill checks or ability scores, so any other penalties would be left to your judgement as DM after considering the situation. For example it could be hard to use a spell that needs the arcane focus and an additional material, but I think it could be worked around with some cunning.
If he lost his left arm, he would get a lot of "he's all right" jokes, besides the obvious attention a missing limb would draw in most contexts.
