Try to develop a kindness for yourself. Practice talking to yourself kindly and not being so self-critical. With practice, you'll naturally start to think less negatively about yourself.
You can start off by smiling and saying hello, then by introducing yourself to anyone you don't know ("Hi, I'm [insert your name]; it's nice to meet you). You can...
Practice mindfulness. Mindfulness can help you become more aware of your thoughts and feelings. Once you become more aware of your negative self-talk, you can practice being kinder to yourself.
The first step is to acknowledge those thoughts so you can investigate where they come from. Try writing down negative thoughts when you have them so you can notice any...
Try distracting yourself with a fun, enjoyable activity. Make sure that you're focusing on the activity itself, and not on any negative thoughts in your head.
Meet with a mental health professional—they can teach you helpful behavioral and cognitive skills/techniques. You can also reach out to a trusted friend or loved one for support.
Be calm and chill around him and divert your attention to somewhere else - hobbies, schooling, etc. Give him a little space and if he still doesn't like you, then...