Severe pain, swelling and blisters after cryotherapy. Can it heal up without scarring?

Usually. Make sure the physician who performs the cryotherapy is aware of the progress as infection of a partial-thickness cryotherapy wound can convert it to full-thickness which could then leave a scar. Good care of the treated area can prevent this unusual complication.
No scar from Cryo. Cryotherapy if applied properly should not leave a scar. Its a partial thickness meaning (not all the way through the skin) tissue ablation, this therapy is used commonly for skin lesions such as warts, benign skin lesion such as keratosis.
Depends: depth/ care. It depends on the depth wand with blisters it does have the potential for scarring and/or loss of pigmentation if proper care is not instituted such as gentle cleansing with mild (non-antibacterial soap) and Bacitracin or petrolatum dressings. If wounds are healed within 10 days scarring should be minimal. Avoid sun exposure to area while healing.