I cant breathe clean air in my own home help please. Is a hepa filter the answer?

Just moved to this great place I am so happy with!
The only problem is and its a HUGE PROB. It is a townhouse and the neighbors smoke.
I am SEVERELY ALLERGIC to smoke and its seeping through he walls. I just had surgery. I am diabetic and have NASH a non alcohol related liver disease and part of the reason I moved was to be in a better place to get healthy again. This is a huge blow to my recovery and adding new health issues.
I cant and don’t want to move from here and although its in the contract that there is no smoking the people next door do not see why they should abide by the new contract since their old one stated smoking was discouraged.
I just dont know what to do. Its disgusting and ailing for me to walk out of my home and stink of smoke,my hair my clothes everything I own. I also have concerns for my son.
It reduces me to tears.
I coughed all night,my eyes burn my head pounds my throat is raw,my skin feels tight and burns my lips burn, Im dizzy,my lungs hurt and that was just the first night.
Please help me remedy this.
THE QUESTION IS:
What can I do to clear the air inside my home?
I have purchased a hepa filer. Its was and hoped that it would help. I had it in my room with the door closed but it did not help.
I cant afford to furnish every room in the house with a large 0 air purifier and why should I have too. I am sad and feel sick and at a loss. What can I do?
Will having these things even be effective?
Please advise….thank you