Now market is pumping like crazy,its obvious we won't go back to 18k or below.
What do you mean by this? I don't see a crazy pump currently because it's just a minor increase and still uncertain if this will continue or might follow by correction. I will not call this a crazy pump unless the price break the resistance level which is not happening for months.
Therefore the price can move downward again if the bear season is not over yet. If you're going to buy back at cheap price then you can wait a bit for much lower price or buy at the current price if you afford it because we'll never know the next movement of the market.
I think he sold bitcoin at 18k and waited for a decline to buy but in the end, things didn't go as he predicted. Bitcoin has not fallen further and is now trading above $20k, he is regretting.
Bitcoin is recovering but it can be seen that this is only a small rally and this has happened a few times this year as well, I also believe bitcoin will correct back soon as economic news, war will affect it. We are still in the crisis period of the world, so it will be difficult to get a sustainable uptrend from now on.
OP, you still have a chance to buy bitcoin at the price you sold it, you can also buy now and DCA when bitcoin corrects or you can wait for bitcoin to correct then start buying, still nothing is too late or regret.