What Causes Persistent Squishy Lump On Forehead Of A Child?

My son had a cd shelf fall on him, it hit his head first then the bed. It didn t fall completely on him. He cried for about a minute and then seemed fine. I called the doctor right away and they said it didn t seem like something to come in for since he was acting normal. The next day a big squishy bump was on the side of his head, so we went to the doctor right away. Again they told me it was fine to watch out for vomiting etc. the next day he woke up puking every where. So I rushed him back in and they told me it was the flu. Which seemed weird cause he didn t have a fever or seemed sick? But I treated it like the flu. And now it s a month later and he still acts like himself but that squishy bump is still there but smaller ? Should this have gone away by now ??