Dear, Well the skin at the tip of penis is very tender and sensitive. therefore, any rough handling can lead to minor abrasions, that are not so evident to naked eye, however that causes burning sensation an dull pain. The kind of experience you suggest through your history of encounter strongly suggest a possibility of such minor abrasion. I would advice you to ignore the pain and give some rest, as in avoid masturbation or sexual intercourse for next week and I guess things will be all fine. Remember any sort of unprotected penetration or oral sex always carries a risk of std. But there are no such complaints suggestive of std appears to be present in your case currently. So don t worry. Hope to have satisfied your worry. Welcome for further queries and stay healthy. Thanks