It’s not racist at all, as there is no negative connotation. It comes from the effect of practising martial arts (many of which originated in China), and which cause burns from holding the arm or leg of the person who has just been thrown, in 1-1 combat, where the person who has been thrown and is held tries to twist out of their grip. (You wouldn’t associate verbal negativity in reporting a graze, for example, but a Chinese burn is a stretch-graze, so the cause is different from a scrape)
There is a similar claim about racism in the term “Indian Summer”, but there are no confirmations cited about this being racist, either, just an incorrect conflation with another term (which can be perceived as derogatory): “Indian Giver” - which means someone who gives a gift, then takes it back later.
I suppose if anyone takes offence at either of these, you could use “martial arts burn” or “second summer” as alternatives - but language used in cases where there is no proof of any historic negativity shouldn’t be always censored, just in case someone (of the hard-of-thinking mentality) might misinterpret it because they haven’t bothered to check facts…