You must first be fully informed yourself, before you are able to inform him.
The various types of genital HPVs (that cause wart-like lesions) may remain in our body for weeks, months or even many years after the initial infection.
HPV-induced inflammatory lesions are usually subclinical, meaning that they are not visible to the naked eye. Only genital warts are visible. Subclinical lesions can stay on the skin and the mucous membranes of the genital organs and the perianal region for months or even years. They regress when our immune system manages to suppress the virus. There is a possibility of reappearance if our immune system becomes weaker for any reason during our lifetime (due to stress, certain medications, etc). Therefore the majority of individuals infected by HPV are not aware of it, nor can they know when they were infected. Of course, this means that they transmitted the virus to their sexual partner at a time when inflammatory lesions were present.
In a monogamous relationship diagnosis of HPV infection usually creates a problem in the couple’s relations. Once the infection is diagnosed in one of the two partners, the other partner worries about the possible existence of a third person.
But discovery of HPV infection simply means that the person was infected sometime during his or her lifetime. No one can know exactly when or by whom. Furthermore, no one can know which of the two partners infected the other (except in the case where one of the two had no prior sexual activities). We cannot therefore know if the inflammation caused by HPV, which you have now been diagnosed with, is a recent or an old one.
If your partner happens to be your first sexual partner, it is almost certain that he transmitted the infection to you. In most cases however men do not know that they have been infected by HPV. Only men who have developed genital warts in the past know about it. The others are unaware, since they usually have no symptoms or visible lesions. Some men may suspect that they have contracted HPV because it was diagnosed in previous partners (if they were told about it).
If you have been diagnosed with HPV now, but you previously had other partners, it is impossible to know who infected you. You may have had the infection, which was simply not diagnosed in previous testing. Pap tests are not 100% accurate. And even if you did have an HPV test and its results were negative, this simply means that at that given time the cells of the uterine cervix were not inflamed by the virus. You cannot know at which times during your life you had an active infection by one or more types of HPV, or if the inflammation diagnosed now is a recent one or the recurrence of an old one.
So you should not worry. HPVs cannot develop into cancer of the uterus in a very short period of time. The inflammation must remain for years for cancer to appear. If you are regularly tested you are safe because premalignant lesions are identified and treated through the tests available to modern medicine (Pap test, HPV-test, colposcopy, biopsy, etc).