If you think that you might have put yourself at risk and been exposed to HIV then you might benefit from taking Post-exposure Prophylaxis (PEP).
PEP is a treatment of anti-HIV drugs that must be taken within 72 hours of exposure to combat the virus, but there is no guarantee that you won't become infected.
If you are worried then contact your local GU clinic and talk about PEP with the doctor. Alternatively, you can go to your local hospital's Accident & Emergency Department, which will be open at weekends. There may be some very unpleasant side effects, and treatment lasts for a month, so taking PEP really isn't a substitute for using condoms.