Is this chin ptosis/witches chin? Chin implant removed 10 days ago. Is it permanent? Any chance shrink back with time? (Photos)

At 10 days after removal of a chin implant, there would still be some expected swelling present that will alter the true appearance of your chin.  It will take several months for the swelling to resolve.  I would say the chances are excellent that the appearance of your chin will return to how it looked before you had the implant placed.  

 Hi, I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.  From the photos, the chin is still very weak and the bit that appears to be chin ptosis (mentalis muscle is at a 45 degree angle off of the chin) could very well be swelling at 10 days post op.  I'm sorry to hear that you had the implant removed at 2 days post-op which would have been well before any determination could have been made regarding the aesthetic results of the size small EAC chin implant.  Using a small, curved incision under the chin to place or remove a silastic chin implant is the least invasive method which should result in very minimal swelling, bruising and recovery time.  You may want to ask your Chin Implant Surgeon about ice therapy and wearing a chin strap over the next couple of weeks to help things settle.  Once everything settles down your chin should return to the pre-operative size and shape.  Ptosis should not be created with a chin implant removal in the scenario that you describe if there was no ptosis present pre-operatively.  When the chin is weak, this creates an imbalance making the nose appear larger, the mid face top heavy, the lower face looks short, de-emphasizes the lips and allows early formation of a "double chin".  
 The silastic chin implant adds forward projection to the chin thereby creating harmony and balance to the lower face.  Using the same incision, liposuction can be performed to reduce the fat and further shape the neck.  Excess skin, from below the chin, can also be removed through the same incision.  
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty.  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  Hope this helps.