If the pen tip is only slightly crooked, you can try to straighten the pen tip yourself. Needle nose pliers can be used to repair this.
If you cannot straighten the nib yourself, it is recommended to go to a pen store and ask a professional to repair it.
Since there is no separate nib for sale, if it cannot be repaired and this pen does not mean much to you, it is recommended to buy another pen.
Extended information:
A fountain pen is a writing instrument that mainly uses metal as the pen body. It holds ink (mostly black or blue) through a hollow pen tube. Gravity and capillary action, and then writing through the duckbill-shaped pen, the writing is light and heavy, and it can be said to be a writing tool for Western calligraphy. The ink in most fountain pens is refillable, usually using an eyedrop vial or a straw to refill the ink.
Reference materials:
Fountain pen? Baidu Encyclopedia