OP - Does the stroller have a guarantee? Ask the manufacturer as well as the place you bought it as some damage is easily repaired free of charge. A proper repair service may also repair the damage for a modest amount. (I'd ask a shoe repair service).

The manner in which you complain will impact the chance of success. Initially the tone should be cooperative and friendly. A request for compensation should be based on an invoice for actual repairs. Note that if you don't get anywhere you can have a lawyer write a short, dry message with the "ask" instead of yourself, as this sometimes has the desired effect. If you threaten legal action you can be very sure that OS customer service (like all other airlines) will no longer entertain your claim. Instead they will let legal deal with it.

In your case I fear it is too late and I would let this one go.