bryanc_74 saidYou likely compressed the ulnar nerve either at the elbow (if you were leaning on them during your ride) or at the base of the palm of your hand as it travels from your wrist into your hand. If it doesn't start improving in a couple of weeks to a month, see your physician.
Follow this advice.
This is common among cyclists, but getting this degree of numbness after two days is unusual. If you Google for it, you'll find a number of articles that describe the condition and what you can do to combat it.
The first thing I'd recommend, if you have not done it, is to make sure you have your bike professionally fit. You need to make sure that your saddle is the right height and distance from your handlebars so you're not putting more weight on your hands than you need to be. Anyone doing a great deal of riding MUST get their bike fit for them by a professional that knows what they're doing. Go to a good bike shop and ask for a recommendation.
For myself I found that I had less pains on the bike (back pain, shoulder strain, hand pain) when I worked on strengthening my core. The stronger your core is the better you can hold yourself on the bike.
Last there are the usual, common sense recommendations. Wear well padded gloves. You can also put gel pads under your handlebar tape, which I've done. Vary your hand grip often.
Oh and congratulations on the ride. Back to back centuries is something to be proud of.