How to add certificate with just key and csr

Hi all,

I am new to Kong. The client I work for generated just the CSR (certificate request) and the private key file for me. Can I use just this to upload certificate to kong gateway? When I use the Kong certificate Admin UI (from console), I get an error:

[schema violation (cert: invalid certificate: x509.new: asn1/tasn_dec.c:309:error:0D07803A:asn1 encoding routines:asn1_item_embed_d2i:nested asn1 error)]

I see that there is a way to generate certificate by using openssl if CSR file and private key are available. But it will be like a self signed certificate then, isnt it? Can I still use it in my project?

Thanks,
Anand