So maybe my explanation was to vague. My put option got exercised from my broker because I forgot to sell it. This means yes I was the put buyer and I had to buy the 100 shares from tesla 100x $180 = somewhat around 18k. But I didn't have 18k balance on my account so my broker lended me 18k. The problem was that if Tesla would have opened higher than my puts strike price was I would have lost big. Luckily it opened red.