Just yesterday afternoon, I got a new cat around 1 year 2 months, lets call him Bean. I also have another cat that has been here for 2 months, lets call him Leo. So far everything was going fine, in fact Bean did not hide under the bed a lot, and he seemed open and let us pet him, which should be good. Now fast forward 4 hours. My mom had just been in my room and she was about to leave, but then suddenly Leo slipped through the door and into the room. This is the first day I got Bean by the way. They both hissed and yelled each other, but luckily they did not attack each other. We managed to get Leo out the door, but Bean is still on edge. I went to sleep, and woke up the next day. I go in to check on him, and now he makes this chewing motion with his mouth whenever I come close, and he also hisses even when I come close. He doesn't hide under the bed too, he just lays out in the open, I don't know if this is normal. What should I do?