No one likes getting a splinter. They can cause infections and even tetanus. Getting a splinter is not a medical emergency but to many people it feels that way. If you have a deck and that deck has splinters then you can get rid of them and even stop the wood from splintering further. But if your deck is very old it may not be preventable. In this situation the deck has got to go.
Decks can get splintered very easily and for a number of reasons. If the wood was splintering when it was installed then that would help it splinter further. If the wood is old then splinters are natural. Old decks have been beaten for years, even decades by the sun by the wind, rain, snow and rapid temperature changes. A wooden deck is not meant to last forever, like the house itself it can only stand for so long. The best way to deal with a splintery deck is to repair it or tear it down and build a new one.
If your deck is still young, five years or less since it was built, and you are suffering sever splinters then you will need to either call back the builders or get rid of the splinters yourself. If there are not many then you can chip away at the area with a chisel until the splinter is gone and then sand the area down well. Fill the hole with wood filler and some of the wood dust that came off the sanding and press it into the hole. Smear it out with a putty knife and leave it to dry. This will seal over the splintering area and stop it from splintering further.
If the deck is splintered everywhere then you will either have to sand and repair the entire deck or tear it down. You could just wear shoes on it but what is happening is a sign of age. As the wood age it gets weaker. Humans are very heavy and when we walk we warp the wood. This happens over and over and with time and weather and sunlight the wood begins to bend too much and then splinters start to form. If your deck is so old it is full of splinters you need to have it torn down and replaced.
If you have a splinter it can often be removed with a pair of tweezers. If the splinter is large and if the wound is bleeding or bleeds a great deal after it is removed then call emergency services as it may have struck a vein or artery. If the splinter is in very deep you should not go in to get it. You should coax it out with a combination of epsome salt baths and hydrogen peroxide. Baking soda and water work well and so does honey.