Welcome to HCM
After going through history it is possible to have murmur and no significant heart disease
so do not worry,as Echocardiography
is very accurate in good hands even colordoppler study may be performed to detect any trivial abnormality.
It is important for you to have medical check up as you are athlete in which cardiac endurance is very important.
Other medical condition must be checked like anaemia
and thyroid disorder
Some murmur are produced just by a flat chest so get a cardiological examination and also plan for a TMT to see your exercise tolerance and check you are fit to take up athletics as comptition and become a professional athlete.
Good luck to you