I can be associated with the flu
, because when flu is there there is chances that you can cause injury
into your nose while cleaning and this can lead to blood in the mucus coming from the nose. Now depending upon the severity of the injury the bleeding amount can vary.
But accoridng to your descrption this problem is with you for long time after you have suffered from the flu, this long duration bleeding in your case can be something more than just the injury which can cause blood in mucus for few occasion and once the bleeding point is healed it will not cause bleeding.
So, for this long term blood coming with the mucus need to be addressed and I would suggest you to consult some ENT surgeon and get examined to make sure this is not something different is causing this.
Thanks and take care.