What does he mean by saying this ?

Question

i can care if you let me know ?

Answer 1

It means he wants you to let him in, know what's going on, and he wants to help you. In other words, "I can't know unless you explain it to me."

Answer 2

It might depend on who is doing the "saying", but my best, blind guess is that he can't read your mind, but he would care if you just tell him what's going on.  "I can care about what you care about if you tell me what you care about."  Does that make sense?  Or, if you let me know what's bothering you.  In a man/woman, boy/girl relationship, it's very typical to have one or both "in the dark" simply because we're too different and think differently.  Hope I'm not getting too philisophical for you.  Good Luck.