In 2016, At the age of 19, Grønning was promoted to the first team squad of AaB and concomitantly signed his first professional contract with the club.[1]
On 19 July 2019, Skive IK announced that they had signed Grønning on one-year contract.[6] He ended the season as Skive's topscorer with 14 goals ind 31 league appearances.
Viborg FF
After a strong season with Skive, Viborg FF confirmed on 27 July 2020, that Grønning had joined the club on a three-year contract.[7]
In his first season at the club, Viborg FF won the Danish 1st Division, securing promotion to the Danish Superliga. Grønning finished as the league top scorer with 23 goals in 32 matches, including a hattrick in the final game of the season against HB Køge.
Suwon Samsung Bluewings
On 5 January 2022, Grønning signed a two-year contract with K League 1 club Suwon Samsung Bluewings, with a one-year option.[8][9] Grønning left Suwon at the end of August 2022, as his contract was terminated.[10]
AGF
On transfer deadline day, 31 August 2022, Grønning joined Danish Superliga club AGF on a deal until June 2025.[11] Head coach Uwe Rösler dropped Grønning from the squad for an upcoming fixture against FC Copenhagen on 13 November 2022,[12] and did not return for the remainder of the year.[13]
OFI
After five months in AGF, Grønning moved abroad once again, this time signing a deal with Super League Greece club OFI until June 2025.[14] Half a year later, in August 2023, the parties terminated the contract, reportedly due to Grønning not receiving his salary regularly.[15]
Castellón
On 17 August, seven days after parting ways with OFI, Grønning joined Spanish Primera Federación side CD Castellón.[16] Although the club did not disclose how long a contract the Dane had signed, several sources reported that Grønning had signed a one-year contract with an option for a further year.
FC Ingolstadt 04
On 31 January 2024, Grønning moved to German 3. Liga side FC Ingolstadt 04.[17] On February 4, 2024, Grønning made his debut for Ingolstadt when he was substituted after 39 minutes in the league match against Dynamo Dresden. Just 7 minutes after his substitution, he scored his debut goal.[18]