I just had a slip and fall at Wal-Mart. What should my next step be?

What you can do if you simply "have some cuts and am very sore" is effectively nothing legally. Forget about the fact that this is a "national retail chain store"--the size of the business has nothing to do with your case--only the facts of the situation and your injuries and losses matter.
Let us assume that the store was liable in having the clear slime in the toy section, though that is not actually a given: if you sue, you'd have to prove that the store was unreasonably careless in causing or allowing the slime to be there. If the slime dripped a few minutes ago and nobody reported it to be cleaned up, they may not be fault: the store has to take "reasonable" steps to keep customers safe, but that does not mean they are obligated to eliminate all risks instantly. They are given a reasonable time to notice the risk (or be notified of it) and fix it, so if the condition was recent enough, they might not be liable.
Even if liable, you can only recover compensation for your provable out-of-pocket medical costs, lost wages (if any) from not being able to work, and, for serious, long-lasting injuries causing significant life impairement for, typically, months or longer, some amount for "pain and suffering." If you are only sore and have some cuts and did not incure large medical costs, there is very little, if any, money you'd get in a lawsuit, so suing makes no sense--you'd  likely spend more on the lawsuit than you'd get back.