Tested with one step-rapid screening test, how reliable?

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The question is not the reliability of the testing method. It is the timing of the test, which determines about your HIV status.

With regarding to HIV testing, the later the test is done, the more reliable the test results will be.

The ELISA tests are highly accurate tests with a very high sensitivity of above 99.9. But they should always be done after 4 weeks after a possible exposure. This is due to the fact that HIV antibodies present only after 4 -6 weeks in about 90% individuals, and almost 95 - 99% of infected individuals produce the antibodies within 12 weeks of exposure. Hence testing for HIV is recommended at a interval of 4 weeks, at least upto 12 weeks (3 months).

In your case, if you think, you might be exposed to HIV, you should repeat the test at 12 weeks after the exposure. If this test is negative, then you can be sure that you are HIV negative.