What does it mean when a man says "you hit my heart"?

I have a colleague and we always have a friendly argument. Of course, I grew to like him and I decided to drop him an email to just clear this bugging feeling in my heart. Over the next few days, I wasn't sure if he had even opened my email and I told him to delete an email that I sent because the email contained a virus. He said it should be fine if he doesn't open and he does not want to delete the email either.

So few weeks later, both of us had to attend a seminar. We were talking about work and he said that the workplace is such a hostile environment. I told him to make a complain to the boss. He said he would be complaining that I hit his heart. I was a little stunned by the words as I was pretty unsure of what he meant and gave a playful punch to his arm and asked if that kind of physical hit was what he meant. He then asked me as to which part of the line that I do not understand. Then, he just looked down to the floor, played with the handle of his bag and was smiling from ear to ear. Later on, we hang out and I asked him if I had said something to offend him. He said no. Then, I asked him to clarify what he meant earlier. He said that since I can't take jokes, he would not joke with me again next time.

So 3 days later, I ask him again as to what he meant. I told him that I check with a friend and she told me it sounds like he likes me. He replied that he meant "hit my heart" as in to cause pain. I then replied him that he hit my heart too always. And he says, it is good for him to know.

So the question is: why does he even say "you hit my heart" and what does it mean?
What does it mean when a man says "you hit my heart"?
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