Head Injury - 2 years old

Hi Doctors, my son recently fell down from a 2 feet height bed with his head first hit the floor. He also has past history of slipped or fell down several time also with his head hit first. I looked for any sign of internal bleeding or serious injury like vomit, dizziness, seizures etc. No signs until today but I find that the size of his head is quite concerning. He actually was born with big head size, went through follow ups with paed for possibilities of Macrocephaly and thank God he is negative based on all the developmental test. So I do not know if I should be worried about his head or not because its hard to detect any swollen part and his head is naturally big in size. He is active, interactive, his memory is good and does not complain for any pain till today. He started speaking clearly at the age of 2 years and he is now 2 years and 8 months. I am very worried if the impact on his head show later when the things get serious and not much I can do. I did some reading on MRI scan. Since it does not have any side effect to the brain (unlike CT scan), I am considering to opt for it.
Can you please enlighten me, at what point should I actually be worried, what I should look for from him, what should I do when that incident already happened, how many percentage similar incidents shows its serious impact after some times and what are the possibilities?

I really thank you in advance for your time and help.

Thank you