As stated earlier, normally if it’s the outer (little finger) side of your hand it’s likely to be the ulna nerve so should settle down after a few days. Whilst there are grips & gloves designed to help prevent it it may not be the hand that’s the actual problem.
I’ve been getting numbness in my right hand for years which had been attributed to the ulna however, after a number of tests it became apparent that the ‘damage’ wasn’t actually in my hand at all but was referred from an old shoulder injury – the ulna runs from your neck down to your hand.
By riding much further than normal you’ve probably just battered it enough to cause a bit of inflamation in there so some ibuprofen may even sort it for you. If you whacked your elbow or shoulder that may also be the cause but then the same ‘treatment’ applies.