Query regarding HIV combo test. It true?

I was injected mistakenly by a contaminated needle on 27th June 2019 at a clinic . Doubting the needle's cleanliness I went for a HIV comb test after 56 days of the administration of the needle from my nearest ICTC centre. The test result were negative. So should I go for the test again as the staff at ICTC centre told me that if there is a direct contact with infected HIV blood then it shows up on the blood report after 28 days but in my case it has been 56 days and the report is negative. But I want to get a specialist advice in this case. What should be now done ? Which test should be done? Is 56 days enough to form a conclusion as they said that HIV transmitted by sexual activities takes more time to show up on blood reports but not HIV transmitted by HIV contaminated blood in a needle. Is it true ?