Owch poor boy that looks sore!
Is he dragging both legs or just the one that's damaged?
Hopefully if it's just that one it's being dragged because of the pain, if it's both legs being dragged then as the others have suggested it could be a spinal/nerve problem.
This would be more of a serious issue in that case, but Betsy above has successfully treated her Christian for an unexplained, sudden onset paralysis.
Christian was at emergency vet appointment this morning!
Please keep him on a soft clean bedding until it's healed up, preferably vetbed or if not fleece on top puppy pads.
Also if you keep him confined in a small'ish area so he can't do more damage to himself. If it is spinal/nerve related.
Looks like he'll need painkillers & quite a high dose of them.
Loxicom is the usual one prescribed. There's dog & cat versions (the dog one is 3x stronger) make sure you question the vet that they've given you the higher or maximum dose for the version they've prescribed.
As he's a newbie youngster, was he kept on wire or meshed flooring where you got him from & possibly caught his toes in that, or in a cage that he's tried to climb up & caught it in that?
Please see a Guinea savvy vet, there's the recommended vet locater on here in the menu/on toolbar which will help you find the best one in your area.
Please go very careful if you have to bandage his feet, as they mustn't be done too tight or this will create a new set of issues & the wound looks like it will need to breath, although it must be kept clean & free of infection too.
He may be prescribed an antibiotic such as Baytril to fight any infection.
although this could cause a lack of appetite & gut mobility problems, but pre/probiotics 1.5-2hrs after the antibiotics will help keep his good gut bacteria at a healthy level & reduce the risk of digestive problems too.
Have a look at the links Wiebke has provided ref syringe feeding & young Guineas if u do need to assist him in feeding safely they're very useful & informative guides.
Try & feed items such as red bell peppers to keep his vitamin c levels up & cucumber to keep him hydrated if you can.
Also if you ask the vet to check for lice & mites too, to make sure he's not just been scratching because of them and caught his feet/toenails that way?
There's nothing to suggest your baby should be PTS & there are options to explore before you even have to consider it.
If a vet suggests it as an early option, then please find another vet quickly!
Keep us updated & hope you can get him sorted. It may be a long process though.
Keep up your good work & TLC
Healing vibes being sent your way for a full & speedy recovery.

Love the girls & I xx