Hello
Based on the facts that you have posted it appears that your wife gets what is called as Dyspareunia .It may be due to dry vagina or discrete vaginal secretion which is necessary for lubrication of vagina and easy penetration of erected penis.or due to vaginismus This can be confirmed only on clinical examination
Please consult qualified Gynaecologist for clinical and per speculum examination and advice.
It is most unlikely to be due to your wide erected penis as well lubricated vagina is capacious enough to accommodate hard erected male penis.
Dr.Patil

hi there,
am dr.surendran
nice to meet you here in HCMagic
Dyspareunia is painful sexual intercourse, due to medical or psychological causes. The symptom is significantly more common in women than in men, affecting up to one-fifth of women at some point in their lives.
mostly due to vaginismus
remedies
Clearly explaining to the patient what has happened, including identifying the sites and causes of pain. Making clear that the pain will, in almost all cases, disappear over the time or at least will be greatly reduced. If there is a partner, also explaining to him the causes and treatment and encouraging him to be supportive.

Removing the source of pain when needed.

learn about her body, to explore her own anatomy and learn how she likes to be caressed and touched.

Prescribing very large amounts of water-soluble sexual or surgical lubricant during intercourse.

Discourage petroleum jelly. Moisturizing skin lotion may be recommended as an alternative lubricant, unless the patient is using a condom or other latex product. Lubricant should be liberally applied (two tablespoons full) to both the penis and the orifice. A folded bath towel under the receiving partner's hips helps prevent spillage on bedclothes
after all understand each other ,have an happy life
hope helped your query
regards dr.surendiran hcmagic