I have been through this. I was a teenager when I first couple times smoked "the reefers". I became extremely paranoid and had panic attacks throughout the experience and for days after. I didn't know at the time I had anxiety disorder. I tried it again a few years later, same reaction. The anxiety after was terrible BUT IT DID PASS. I learned I have anxiety disorder soon after (and I'm a recovering addict which explains why I continued to do it with bad reactions). I needed therapy and help for my issues, you may just need time to get it out of your system or a doctor/psychiatrist to check for anxiety disorders. What kind and how much did you smoke? This can affect how long it stays in your system. If you're a minor talk to an adult to get support.
You don't say how old you are. The first response wasn't accurate, marijuana isn't an addictive drug and using a drug once doesn't trigger some addictive trick your body plays on you even if you use an addictive drug. There's no need for inaccuracy to believe drugs need to be used with caution whether it's aspirin or marijuana. But you clearly have anxiety or insecurity inside you and it came out while you were high, which is very common. If you hold onto it, it won't go away. If you don't, it will. Some of this depends on whether you have a predilection for anxiety -- does it run in your family? Are you a worrier? So, two things to do now -- relax and know you don't have a brain that can handle this substance so don't use it, and if this continues consider seeing a professional to help you past it. If it doesn't continue, it's still a learning experience but it doesn't mean you're cursed with anxiety forever or even that you'll never be able to use pot, though there's nothing wrong with never using it again. And don't Google symptoms -- ever. You can Google diagnoses and treatment options but don't go googling symptoms.
Your body is looking to get you addicted to the drug don't listen to it.It's not real trust me.The best thing to do is layoff caffeine, read a book and remain calm.The anxiety is in your head , it's a delusion brought upon you by knowing the dangers of drugs. This will pass if you stay strong and fight tempation for some release. :)