please tell me what is this , i had last sex in august 2019
This is a skin problem - the source of these are due to what your penile skin has been in contact with.
Make a list: typically this would be - soap, shower gel, hair shampoo when you take a shower and it drains down to your genital region - include washing powder or other treatments that your clothes are washed in.
You also need to think about anything you may apply to your penis for masturbation - so this would typically be a Lube, skin cream, baby oil or lotion - some men even apply things like hair shampoo directly to the penis for masturbation. You need to think of everything that contacts your penis.
What usually happens is that something changes from what it used to be - such as a change in soap, shower gel, an antibacterial wash - and so on.
Or, as I say, it could even be a change in washing powder, or other treatments your clothes are washed in. Also, for the likes of masturbation, have you recently applied something to your penis you have not used before?
After this, what can happen is the skin at the tip of your penis has been compromised in terms of its healthiness for quite some time - and basically, if this has occurred, simply anything in contact with your penile skin, other than water, will make the situation worse.
If you are unable to trace the cause of this you may need to seek the help of a dermatologist